A b i n i t i o calculations as a source of intermolecular potential functions. Ethanol–water with a minimal basis set

Abstract

The potential energy surface of the (trans)ethanol–water dimer has been explored with ab initio quantum mechanical calculations employing a minimal basis set to obtain a potential function suitable to computer simulations of the relevant aqueous solution. In all, 410 interaction energy values have been calculated. A part of the complex geometries has been produced approaching the water molecule to the ethanol along 17 different axes, and a part with an iterative random procedure. On this data base a fit with the experimental geometry of the water molecule and one with the ST2 model have been performed, with standard deviations of 0.69 and 0.73 kcal/mole, respectively. A limited test concerning the role of the three body term in open chain trimers has also been carried out. Finally, these SCF calculations have been used to check the possibility of the electrostatic approximation and of the pair potential library given by Clementi, to provide reliable intermolecular potential energy values in these kinds of systems.